1. Technical Field
The present invention relates to an optical device, a detecting apparatus, an electronic apparatus, and the like.
2. Related Art
Recently, surface enhanced Raman scattering (SERS) spectroscopy using surface plasmon resonance (SPR), particularly, using localized surface plasmon resonance (LSPR) has attracted attention as a high-sensitivity spectroscopy technique for detecting low-concentration target molecules. SERS refers to a phenomenon in which an enhanced electric field is formed between metal particles contained in a nanometer-sized convex and concave structure, and Raman scattering light is enhanced due to the enhanced electric field by, for example, 102 times to 1014 times. In this technique, single-wavelength excitation light such as laser light is irradiated on target molecules. A scattering wavelength (Raman scattering light), which is slightly shifted from the wavelength of the excitation light by molecular vibration energy of the target molecules, is spectroscopically detected to obtain a fingerprint spectrum. Based on this fingerprint spectrum, an extremely small amount of target molecules can be identified.
The intensity of the enhanced electric field is stronger in the vicinity of metal particles, particularly, in a gap between adjacent metal particles. Therefore, it is necessary that target molecules in a fluid sample be fixed in a gap between metal particles. For example, in JP-A-2009-222401 and P. Freunscht et al., “Surface-enhanced Raman spectroscopy of trans-stilbene adsorbed on platinum or self-assembled monolayer-modified silver film over nanosphere surfaces”, Chemical Physics Letters, 281 (1997), 372 to 378, a self-assembled monolayer (SAM) film is formed on a metal surface of a sensor chip.
In FIGS. 10 and 12 of JP-A-2009-222401, the diameter of a metal pattern is 800 nm. In P. Freunscht et al., a silver film is formed on a polystyrene spherical convex portion having a diameter of 542 nm. Moreover, in JP-A-2009-222401 and P. Freunscht et al., a self-assembled monolayer (SAM) film is formed on a metal pattern.
In JP-A-2010-78482, an organic molecular film and a surface modification layer which have a thickness of 0.3 nm to 50 nm are formed over a metal nanosphere. In JP-A-2008-249434, a fine porous polymer film is formed on a metal surface.
In the structures disclosed in JP-A-2009-222401 and P. Freunscht et al., since the density of the metal particles which form a hot site where an enhanced electric field is formed is low, there is a limit in improving the detection capability in a sensor chip.
In addition, the self-assembled monolayer (SAM) disclosed in JP-A-2009-222401 and P. Freunscht et al.; and the organic molecular film and the surface modification layer disclosed in JP-A-2010-78482 make adsorbed target molecules and metal particles distant from each other. The enhanced electric field hot site formed in a gap between the metal particles is significantly attenuated when measured at positions at intervals of 0.1 nm from a metal surface. That is, in order to achieve high-sensitivity SERS detection, it is necessary for the target molecules to be captured in the vicinity of the metal surface.
Meanwhile, in a thiol-based silane coupling agent used in JP-A-2008-249434, regular holes with a size of 10 nm or less which can capture volatile organic compound (VOC) molecules cannot be formed. The assumption in JP-A-2008-249434 is that the hole size is 10 nm to 100 nm (0060). Since this hole size is too large to capture VOC, sufficient detection sensitivity is not obtained. In addition, the porous polymer film disclosed in JP-A-2008-249434 does not include complete through-holes through which a metal surface is exposed. From this point of view, in JP-A-2008-249434, similar to other techniques of the related art, since the enhanced electric field hot site is attenuated at a position distant from the metal surface, there is a limit in improving detection capability.